Effects of new anticancer drugs on cell cycle progression of L1210 murine leukemia, Friend murine erythroleukemia, Chinese hamster ovary (CHO) cells and on normal human lymphocytes stimulated by mitogen, in cultures, will be investigated. The recovery rates from drug treatment in relation to cell cycle (including quiescent vs. cycling cells), drug effects that may be either cell type- or tumor-specific, effects on cell recruitment from quiescence into the cycle (and vice versa), and effects on cell differentiation will also be analysed. Furthermore, the possible mechanisms of drug action will be investigated by analysing their effect on RNA synthesis and RNA content per cell, chromatin structure and cell morphology. In selected cases drug interaction with natural and synthetic nucleic acids will be studied. Flow cytometry, supported by autoradiography will be the main method of analysing cell cycle effects. Electron microscopy, biochemical and biophysical methods will be used to study mechanisms of drug action. In addition, we propose to further develop flow cytometric methods for the analysis of drug effects and to continue research on intracellular factors related to regulatory mechanisms of the cell cycle that may be possible targets for drugs.